This invention relates to signal conditioning systems, and in particular to a signal decoder with adaptive signal weighting.
Various techniques for encoding and decoding a data signal (e.g., video or audio) are known. For example, U.S. Pat. Nos. 4,101,849 and 4,136,314 disclose an encoding technique that compresses the data signal with high frequency preemphasis. The signal is then stored or transmitted onto or across a medium, and the received data signal is expanded and deemphasized in a complementary manner. Preemphasis involves altering the magnitude of select frequency components of the signal with respect to the magnitude of frequency components, to reduce noise and thus improve the signal-to-noise ratio (SNR). Similarly, deemphasis involves altering select frequency components of a received encoded signal (e.g., a signal that was transmitted across a communication channel or read from a storage medium), in either a negative or positive sense in a complementary manner to the preemphasis applied to the signal.
U.S. Pat. Nos. 4,101,849 and 4,136,314 disclose controlling the amount of preemphasis as a function of the ratio of the energy in high and low frequency portions of the data signal. Of course the amount of deemphasis is also controlled by the ratio of the energy in the high and low frequency portions of the signal. However, a problem with this ratio technique is that it does not efficiently use the bandwidth of the transmission channel or the storage medium.
U.S. Pat. No. 4,539,526 discloses an adaptive signal weighting system for encoding and decoding a data signal. The technique disclosed therein preemphasizes only the high frequency signal components during encoding as a function of the spectral energy contained in the high frequency portion of the signal. On the decoder side the received signal is deemphasized in a complementary manner by providing a gain to the high frequency signal components based upon the spectral energy within the high frequency portion of the spectrum of the received signal. One problem with this technique is that it controls the amount of preemphasis/deemphasis based upon the spectrum of only the high frequency components.
Therefore, there is a need for an improved technique for encoding and/or decoding a data signal that is transmitted across a data channel or stored and retrieved from a storage medium.